The present invention is directed to a conductive polymeric nanocomposite material incorporating uniformly dispersed vapor-grown carbon nanofibers, and to a method of forming such a nanocomposite material.
Vapor-grown carbon nanofibers are a unique form of carbon produced by a variation of a vapor-phase catalytic method in which a carbon-containing feedstock is pyrolyzed in the presence of small metal catalyst particles. The resulting nanofibers typically have an outer diameter of 60 to 200 nm, a hollow core of 30–90 nm, and a length on the order of 50 to 100 microns.
The use of vapor-grown carbon nanofibers has been proposed for providing improved mechanical, electronic and thermal transport properties to polymers. For example, vapor-grown carbon nanofibers have been dispersed in polymer matrices by a polymer melt blending method in which the dispersants in the polymer matrix are mechanically sheared apart. See, for example, U.S. Pat. No. 5,643,502. However, as most polymers are incompatible with carbon nanofibers, it is difficult to achieve uniform dispersion of the carbon nanofibers in the polymer matrix. In addition, the high shear mechanical blending can result in the breakage of the carbon nanofibers.
Accordingly, there is still a need in the art for an improved method of reinforcing a polymeric material with carbon nanofibers to produce a composite which has maximum attainable improvement in various mechanical, electrical, and thermal properties.